Living world

• Ecosystem


  A community of plants and animals that interact with each other and their natural environment
• Components of an ecosystem

  • Biotic (living things: plants, animals, bacteria, fungi)
  • Abiotic (non-living things: soil, rocks, sunlight, rainfall)
• Example of a small-scale ecosystem in the UK

  • Pond
• Food chain


  Shows the direct flow of energy and nutrients from a producer to a consumer
• Producer


  A plant that makes energy through photosynthesis
• Consumer


  An animal that eats another plant or animal for energy
• Food web


  Shows the links between multiple different organisms and different food chains
• Decomposer


  Breaks down dead plant and animal material to return the nutrients back to the soil
• There are often not more than three or four links to a food chain as there is not enough energy to support another level
• Trophic pyramid


  Shows the energy loss through a food chain
• Reasons for energy loss in a food chain


  • Not all the organisms is eaten (feathers, bones)
  • Energy is lost through movement
  • Energy is lost through respiration
  • Energy is lost through excretion
• Nutrient cycle


  Nutrients are recycled round and round an ecosystem
• Stores in the nutrient cycle

  • Biomass: total weight of all living organisms (plants and animals)
  • Litter: dead plant and animal material
  • Soil
• Inputs to the nutrient cycle

  • Rainfall can bring nutrients into the system
  • Rock beneath the soil can be broken down (weathered) creating soil and adding nutrients to it
• Outputs from the nutrient cycle

  • Surface run-off: the flow of water over the surface of the ground including rivers which can carry away litter and therefore nutrients
  • Leaching: when there is heavy rainfall that washed through the soils and strips it of nutrients
• The nutrient cycle is a good example of a recycling system but it is not perfect
• If dragonflies go extinct

  In the short term there would be a decrease in fish and an increase in mosquito larvae. In the long term, there would be a decrease in heron and a decrease in algae.
• If mosquitos went extinct


  In the short term there would be an increase in algae. In the long term this would mean that oxygen within the pond is used up by the algae (eutrophication) which means that other animals would die.
• Natural changes to an ecosystem

  • Droughts
  • Forest fire
  • Animal migration
  • Hazards
  • Disease
• Drought


  Can affect the water level, cause loss of habitats, and lead to desertification
• Forest fires


  Can destroy habitats and wildlife
• Human causes of change to an ecosystem

  • Fertilisers and pesticides
  • Deforestation
  • Urbanisation
  • Climate change
  • Pollution
  • Introducing species
  • Overfishing
  • Draining ponds
• Biome


  Large scale global ecosystems usually named based on the dominant vegetation, largely influenced by the global atmospheric circulation system
• Smaller scale variations in biomes can be affected by ocean currents and altitude
• The main types of weathering are physical, chemical, biological
• Physical weathering is the breaking up of rocks into smaller pieces without changing their composition.
• Chemical weathering involves reactions between rock minerals and water or air to form new compounds that break down the original rock.
• Erosion is the process whereby material is removed from one place and transported elsewhere.
• Deposition is when eroded materials are deposited somewhere else.
• Solution is when dissolved substances are carried away in solution (water).
• Tropical rainforests contain more animal species than any other ecosystem
• Many indigenous people have adapted to live in the rainforest and they make a living by hunting, farming and fishing
• Plants and soil in tropical rainforests

  • Most of the trees are evergreen to help them take advantage of the continual growing season
  • Trees are very tall and the vegetation cover is dense
  • There's very little light that actually reaches the forest floor
  • There are lots of epiphytes which are plants that grow on other living plants and take the nutrients from the air
  • The soil is not very fertile as heavy rain washes away the nutrients but there is surface nutrients due to decayed leaf fall
• Climate of tropical rainforests

  • The climate is the same all year round generally between 20 to 28 degrees celsius
  • Rainfall is very high around 2,000 millimeters per year and it rains daily
  • The sun's energy is most intense near the equator as is overhead all year round
• How tropical rainforests are interdependent

  1. Sucropia trees have hollow stems and produce energy rich food at the base of their leaves

  2. Azteca ants rely on the trees for this food and shelter

  3. These ants fight off other insects trying to also feed from the same tree

  4. Without these ants, sucropia trees would be much more vulnerable to other predators
• Adaptations of plants in the rainforest

  • Lianas are woody vines that have roots in the ground but climb up trees to reach the sunlight
  • Tree trunks are tall and thin to allow trees to reach the sunlight
  • The bark on these trees are smooth to allow water to flow down to the roots easily
  • Drip tips on leaves allow water to run off the leaves quickly without damaging or breaking them
  • Buttress roots are large roots which have ridges which create a large surface area that help to support large trees
  • Epiphytes are plants which live on the branches of trees high up in the canopy and get their nutrients from the air and water but not from the soil
• Adaptations of animals in the rainforest

  • The sloth uses camouflage and moves very slowly to make it difficult for predators to spot
  • The spider monkey has long strong limbs to help it to climb through the rainforest trees
  • The flying frog has fully webbed hands and feet and a flap of loose skin that stretches between its limbs which allows it to glide from plant to plants
  • The toucan has a long large bill to allow it to reach and cut fruit from branches that are too weak to support its weight
• Tundra


  • Found at high latitudes above 60 degrees north of the equator in northern europe canada and alaska
  • Winters are very cold
  • Summers are brief
  • Little rainfall all year
  • Hardly any trees but there is moss grass and low shrubs
  • Layer of permafrost on the ground all year
• Taiga (Boreal Forest)


  • Found at mid high latitudes between 50 and 60 degrees north
  • Winters are cold and dry
  • Summers are mild and moist
  • Trees are coniferous which mean evergreen and have needles to conserve energy
• Tropical Rainforest


  • Found at the equator between the tropics of camp francois and cancer
  • Hot and wet all year round
  • Lush forest with dense canopies of vegetation forming distinct layers